Im assuming this is in the context of OneDND/5.5e/6e/etc. So it doesn't belong in house rules.
I think base monk should just remove ki costs from Step of the Wind and Flurry of Blows. Unarmed fighting already has its shortcomings, so its not some wild and out of control thing. And Rogues get most of Step of the Wind for free without it being broken.
Let the investment be their bonus action for that round, and let ki be dedicated to Stunning Strike and powering subclass features.
1) Change monk unarmored defense from Wisdom bonus to Constitution bonus. This helps to build monks that can stay in the fight longer.
2) Change Ki points to be equal to level plus Wisdom bonus. This help to build monks that are more mystical in their approach to fighting.
3) Starting Martial Arts die = 1d6
4) Maximum Martial Arts die = 1d12
This belongs in the house rules forum.
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Im assuming this is in the context of OneDND/5.5e/6e/etc. So it doesn't belong in house rules.
I think base monk should just remove ki costs from Step of the Wind and Flurry of Blows. Unarmed fighting already has its shortcomings, so its not some wild and out of control thing. And Rogues get most of Step of the Wind for free without it being broken.
Let the investment be their bonus action for that round, and let ki be dedicated to Stunning Strike and powering subclass features.
I'd rather see 1d6, 1d8, 2d6, 2d8. This simulates the speed and multiple strikes of a monk without adding more which can make hex or hm OP.